The investigators propose to develop a compact wearable pump-lung to support total respiratory needs in adults with either acute respiratory distress or chronic lung failure. The need for such device is considerable and advancements in materials, biocompatibility, and design have enabled us to develop a promising prototype (chronic artificial pump-lung, CAL). We have combined our clinical experience and bioengineering strengths to propose a design criteria that include: Compact wearable device, oxygen delivery of 250 cc/min, CO2 elimination of 200 cc/min, blood pumping of 5 liters/min, modular design facilitate oxygenator replacement (disposable component), use of oral anticoagulation, and fail-safe flow-regulating control. In operation the CAL will achieve extremely efficient gas transfer by utilizing active convecting mixture of the blood via rotation of discs comprised of microporous hollow fiber membranes. Rotation of the fiber discs draws and pumps blood though the device and over the fibers. To date, compact prototypes are five times more efficient (per m2) in O2 delivery than commercial oxygenators and pump at physiologic flows against anticipated afterloads. Preliminary work on biocompatibility has encouraged us that the device can have an optimized blood flow path, platelet resisting surface, and gentleness to RBC, WBC, and platelets. Specific aims of this proposal are: 1) Evaluate the functional pumping and mass exchange characteristics, in vitro of candidate 0.5 m2 devices in a water-based circulation loop while modeling the flow path of the CAL with computer flow design to predict pumping characteristics and aid in optimization of flow path. 2) Evaluate flow path biocompatibility of candidate CAL designs developed in bovine blood-based circulatory loop to assess hemolysis, thrombotic deposition, and platelet activation. Functional pumping and mass transfer characteristics of candidate CAL prototypes will concurrently be evaluated with this flow loop. In parallel, the CFD model developed in Specific Aim 1 will be extended to blood and refined into a predictive design tool. 3) Characterize the membrane transport and platelet attacking properties of uncoated and candidate siloxane-based fiber coatings. 4) Perform chronic (21-day) in vivo bovine experiments to assess both the gas exchange and pumping functionality and overall long-term biocompatibility of the CAL prototype. 5) Develop and validate a closed-loop, flow control algorithm to ensure fail-safe pumping by the CAL spinning disc(s); incorporate algorithm into a controller unit to be part of the overall CAL system.